The employment of optical fibers for the transmission of information-bearing light signals is an established art. Of primary concern is the efficient coupling of the light from a semiconductor source, such as a laser or a light-emitting diode (LED), into the end of a fiber.
A recent scheme for enhanced laser-to-fiber coupling includes imparting a roof-shaped tip onto the end of a fiber, which roof-shaped tip not only increases the amount of light coupled into the fiber, but further reduces the damaging effects of light reflected back to the source.
Another coupling arrangement was disclosed in U.S. Pat. No. 4,130,343 to Miller et al. This invention addressed the packaging problems in systems which sought to couple light from an LED into a fiber. In this case, a bevel of a certain angle had to be polished onto the end of the fiber.
In the manufacture of these tips onto the end of an optical fiber, it is crucial to maintain good control of the angle of the tip. Further, it is important to produce optically flat, defect-free surfaces to the tip for maximum coupling efficiency and protection against reflected light. It may be necessary to change abrasives during the polishing steps, so as to finish up with a mild abrasive to obtain the smoothest possible surfaces on the fiber tip. Typically, the fiber is held rigid in a fixture in order to accurately polish the desired shape on the tip. However, the fiber end to be polished, which necessarily extends a slight amount beyond the fixture, can be damaged by shock or vibration upon contact with an abrasive, causing chips in the sides of the tip. Chips, or other defects larger than 0.1 micrometer in size are undesirable for efficient coupling.
Therefore, a method to polish a roof-shaped or bevelled tip onto the end of an optical fiber, which provides accuracy and simplicity, as well as optically flat, defect-free surfaces has been sought.